COBOL is a business-oriented language revised multiple times since its original design in 1960. It is claimed to still be used in over 80% of organizations.
*COBOL. Coding like it's 1985. *Compiles with GnuCOBOL in OpenCobolIDE 4.7.6. *COBOL has significant differences between legacy (COBOL-85) *and modern (COBOL-2002 and COBOL-2014) versions. *Legacy versions require columns 1-6 to be blank (they are used *to store the index number of the punched card..) *A * in column 7 means a comment. *In legacy COBOL, a comment can only be a full line. *Modern COBOL doesn't require fixed columns and uses *> for *a comment, which can appear in the middle of a line. *Legacy COBOL also imposes a limit on maximum line length. *Keywords have to be in capitals in legacy COBOL, *but are case insensitive in modern. *First, we must give our program ID. *Identification division can include other values too, *but they are comments only. Program-id is mandatory. identification division. program-id. learn. *Let's declare some variables. data division. working-storage section. *Variables are specified by a "picture" - how they should be *displayed, and variable type is inferred from this. *The "01" value is the level number which is used for building *data structures. 01 myname picture xxxxxxxxxx. *> A 10 character string. 01 age picture 999. *> A number up to 3 digits. 01 valx picture 999. *> Another number up to 3 digits. 01 inyear picture s9(7). *> S makes number signed. *> Brackets indicate 7 repeats of 9, *> ie a 6 digit number (not an array). *Now let's write some code. procedure division. main-procedure. *> COBOL is the language that uses DISPLAY instead of PRINT. *> Note: no full stops after commands. Only after the LAST *> command. display "Hello. What's your name?" *> Let's input a string. *> If input too long, later characters are trimmed. accept myname display "Hello " myname *> We can display several things. display "How old are you?" *> Let's input a number. *> If input too long, EARLIER characters are trimmed. accept age display age *> Left-padded to three chracaters with zeroes, *> because of the defined PICTURE for age. *> We have two ways of doing a FOR loop. *> Old style way: doesn't give an index. perform age times display "*" with no advancing *> Ie, no newline at end end-perform display "." *> Output buffer isn't flushed until newline. *> New style way: with an index. perform varying valx from 1 by 1 until valx > age display valx "-" with no advancing end-perform display "." *> If tests are still good old if tests. if myname = "Bob" then display "I don't like Bob." else display "I don't know you." end-if *> There are two ways of doing subprograms and calling *> them. *> The simplest way: a paragraph. perform subparagraph *> The complex way, with parameters and stuff. call "eratosthenes" using age returning valx display "There were " valx " primes." stop run. subparagraph. *> Marks the top of an internal subprogram. *> Shares variable score with its caller. *> Read year from system timer. *> Remember the whole "year 2000 crisis"? The yyyyddd *> option was added in response to that. accept inyear from day yyyyddd. *> We can do math step-by-step like this... divide 1000 into inyear. subtract age from inyear. display "You were born in " inyear "." *> Or we can just use expressions. compute inyear = 1970 - inyear. if inyear >= 0 then display "When you were " inyear ", " with no advancing else display inyear " years before you were born, " with no advancing end-if display "COBOL was the most popular language in the world." . *> You can put the final . on a new line if it's clearer. *If we want to use a subprogram, we use literally a subprogram. *This is the entire program layout, repeated for the *eratosthenes subroutine. identification division. program-id. eratosthenes. data division. working-storage section. *Declare an array. *We can declare a variable to use as an index for it at the *same time. 01 sieve pic 9 occurs 999 times indexed by sa, sb. *> Standard cobol doesn't have a boolean type. 01 pstart pic 999. 01 counter pic 999. *Our parameters have to be declared in the linkage section. *Their pictures must match the values they're called with. linkage section. 01 maxvalue picture 999. *"using" declares our actual parameter variables. *"returning" declares the variable value returned at end. procedure division using maxvalue returning counter. main-procedure. display "Here are all the primes up to " maxvalue "." perform varying sa from 1 by 1 until sa > maxvalue move 1 to sieve (sa) end-perform perform varying sa from 2 by 1 until sa > maxvalue if sieve(sa) = 1 then compute pstart = sa + sa perform varying sb from pstart by sa until sb > maxvalue move 0 to sieve(sb) end-perform end-if end-perform initialise counter *> To zero by default for a number. perform varying sa from 2 by 1 until sa > maxvalue if sieve(sa) = 1 THEN display sa add 1 to counter end-if end-perform. end program eratosthenes. end program learn.
Originally contributed by Hyphz, and updated by 0 contributor(s).